Surface Mixed Layer Salinity Budget in the Tropical Indian Ocean

热带印度洋表面混合层盐度收支

• 批准号: 1558331
• 负责人: Ren-Chieh Lien
• 金额: $ 18.52万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-02-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558331&HistoricalAwards=false
• 关键词: Surface; Mixed; Layer; Salinity; Budget

The Madden-Julian Oscillations (MJO) is an atmospheric disturbance over the tropical oceans with a recurrence period between 30 and 90 days, consisting of surface westerly wind bursts, deep atmospheric convection, and heavy precipitation. The MJO generally originates in the Equatorial Indian Ocean, develops as it travels eastward at roughly 5 meters per second along the equator until reaching the central Pacific and then accelerates as it circumnavigates the globe, impacting global weather patterns. MJO prediction is unsatisfactory, especially at its initiation stage when the oceanic feedback to the atmosphere may be important. The DYNAMO (DYNAmics of the Madden-Julian Oscillation) experiment conducted in 2011-2012 in the central Tropical Indian Ocean was successful in capturing several initiations of the MJO. In that context, one of the goals of DYNAMO was to understand the effects of salinity stratification on the turbulent entrainment flux and Sea Surface Temperature in the Tropical Indian Ocean where salinity stratification plays a significant role in the heat, momentum and salinity budgets of the surface ocean mixed layer. Observations from the DYNAMO experiment confirm that the turbulent heat flux at the base of the surface mixed layer is a primary component in the heat budget. The turbulent heat flux, however, varies by amounts larger than 100 Watts per square meter at intra-seasonal (e.g., MJO) time scales under similar surface wind and buoyancy forcing, and is presumably modulated by the barrier layer processes. This study will evaluate the details of the surface mixed layer salinity budget and barrier layer properties, and their temporal and spatial variations. Results from this proposed study will quantify and increase understanding of salinity stratification effects on turbulent entrainment fluxes in order to improve parameterizations of turbulent fluxes in the central and eastern Tropical Indian Ocean. This analysis project will complete the training of a Ph.D. student.This project focuses on the surface mixed layer salinity budget in the central and eastern Tropical Indian Ocean and its modulation of Sea Surface Temperature and the evolution of the Madden-Julian oscillation. Comprehensive in-situ observations from ocean moorings deployed in the central and eastern Tropical Indian Ocean as part of the DYNAMO experiment, and remotely-sensed Sea Surface Salinity from the Aquarius satellite will be used for that purpose. The moorings collected meteorological variables, as well as temperature, salinity, and horizontal velocity measurements in the upper ocean. All the DYNAMO moorings and some RAMA moorings were equipped with microstructure sensors, allowing direct measurements of turbulent entrainment fluxes. These observations provide a unique opportunity to close the surface mixed layer salinity budget in the central and eastern TIO during different MJO phases in the period of the DYNAMO experiment. The air-sea salinity flux will be computed using mooring meteorological measurements. The advective salinity flux will be computed using mooring measurements, aided by the Aquarius measurements. The turbulent salinity flux will be computed using direct microstructure measurements. The dominant fluxes in the surface mixed layer salinity budget will be identified. The temporal (from days to intra-seasonal) and spatial (central to eastern Tropical Indian Ocean) variability of salinity fluxes and barrier layer properties, and their effects on shear instability and turbulent entrainment flux will be quantified in different MJO phases. This study will establish the basis for developing a physics based turbulence parameterization scheme that includes the effects of barrier layer process that can help improve model predictions of the initiation and evolution of the MJO.

马登-朱利安振荡（英语：Madden-Julian Oscillations，缩写为MJO）是热带海洋上空的一种大气扰动，其重现周期在30到90天之间，包括地面西风爆发、深层大气对流和强降水。MJO通常起源于赤道印度洋，沿着赤道以每秒约5米的速度向东移动，直到到达太平洋中部，然后在环绕地球仪时加速，影响全球天气模式。MJO的预测是不令人满意的，特别是在它的初始阶段，海洋对大气的反馈可能是重要的。2011-2012年在热带印度洋中部进行的MJO（Madden-Julian Oscillation动力学）实验成功地捕获了MJO的几次启动。在此背景下，热带印度洋海洋观测组织的目标之一是了解热带印度洋盐度分层对湍流卷吸通量和海表温度的影响，在热带印度洋，盐度分层在海洋表层混合层的热量、动量和盐度收支方面发挥着重要作用。DYNAMO实验的观察证实，表面混合层底部的湍流热通量是热量收支的主要组成部分。然而，湍流热通量在季节内（例如，MJO）的时间尺度下类似的地面风和浮力强迫，并推测调制的障碍层过程。这项研究将评估表面混合层盐度收支和障碍层特性的细节及其时空变化。从这项拟议的研究结果将量化和增加了解的盐度分层湍流夹带通量的影响，以提高参数化的湍流通量在热带印度洋中部和东部。这个分析项目将完成一个博士的培训。该项目的重点是热带印度洋中部和东部的表层混合层盐度收支及其对海表温度的调节和马登-朱利安振荡的演变。为此目的，将利用作为海洋观测卫星实验一部分而部署在热带印度洋中部和东部的海洋系泊设备进行的全面现场观测，以及Aquarius卫星遥感的海面盐度。这些系泊设备收集了气象变量，以及海洋上层的温度、盐度和水平速度测量值。所有的CNOO系泊系统和一些拉马系泊系统都配备了微结构传感器，可以直接测量湍流卷吸通量。这些观测结果提供了一个独特的机会，关闭在中央和东部TIO在不同的MJO阶段的TIO实验期间的表面混合层盐度预算。将使用系泊气象测量值计算海气盐度通量。平流盐度通量将使用系泊测量值计算，并辅以Aquarius测量值。湍流盐度通量将使用直接微结构测量计算。将确定表层混合层盐度收支中的主要通量。的时间（从天到季节内）和空间（热带印度洋中部到东部）的盐度通量和障碍层特性的变化，以及它们对剪切不稳定性和湍流夹带通量的影响将在不同的MJO阶段量化。这项研究将建立一个基于物理的湍流参数化方案，包括障碍层过程的影响，可以帮助提高模型预测的启动和演变的MJO的基础。